A common use for crimping devices is to apply couplings to the ends of hydraulic hoses. A common form of coupling consists of a tubular body portion surrounded by a tubular shell portion, with an annular space between them. The end of a hose is pushed over the body portion into the space between it and the shell portion, and then the shell portion is crimped radially inwards to squeeze the end of the hose tightly between the shell portion and the body portion, thereby firmly securing the coupling to the hose.
British patent specification No. 962,094 and Canadian patent specification No. 896,222 disclose prior crimping devices which have been used for this purpose. In both those devices, a set of dies arranged around an axis are located within a crimping member which has a conical tapering inner surface. The outer surfaces of the dies lie against the inner conical surface of the crimping member. In each case an ordinary cylindrical hydraulic ram is employed to produce relative axial movement between the dies and the crimping member such that the dies are forced by the conical surface on the crimping member to move towards each other, thereby crimping a hose coupling located between the dies. In British specification No. 962,094 the dies are axially fixed and the crimping member is driven relative to them by the hydraulic ram. In Canadian specification No. 896,222 the crimping member is fixed and the dies are driven axially relative to it by the ram. In practice, it is important that at the end of a crimping operation the outside of the crimped article should have been brought to a predetermined desired outside diameter. In the British and Canadian specifications referred to above, a pair of gauging members are fixed respectively relative to the crimping ring and relative to the dies. During a crimping operation, the operator of the device has to judge by eye when these two gauging members become in line with each other, and to stop operating the device at that moment. One of the gauging members has to be preset, before crimping begins, so as to ensure that a predetermined outside diameter will have been reached when the two gauging members come into line with each other.
Devices such as those just referred to have various disadvantages.
Firstly, it is typically necessary to apply an axial force of up to 30 tons to effect a crimping operation. Using cylindrical rams as in the prior art, this has frequently required a hydraulic operating pressure of up to 10,000 psi. To achieve the required force with a lower operating pressure involves various design problems and tends to result in a device which is too bulky. The use of such a high pressure means that sealing problems are proportionately great, and a source of such a high pressure must be provided.
Secondly, the gauging members are located well off the central axis of the crimping device and for that reason its accuracy is adversely affected by any mis-alignment or distortion of the components of the device which may occur when it is being operated.
Thirdly, the gauging elements are such that it is not easy to preset them by eye, they rely upon the operator perceiving that the gauging elements have come into line with each other and stopping the operation of the device, in order to crimp down to a predetermined outside diameter, which is not reliable, and there is the construction which involves protruding parts which are relatively easily damaged.